nixos/test: added verbose output for failed tests

nixos/lib/test-driver/test-driver.py

@@ -84,7 +84,7 @@ CHAR_TO_KEY = {
 
 # Forward references
 nr_tests: int
-nr_succeeded: int
+failed_tests: list
 log: "Logger"
 machines: "List[Machine]"
 
@@ -841,23 +841,31 @@ def run_tests() -> None:
             machine.execute("sync")
 
     if nr_tests != 0:
+        nr_succeeded = nr_tests - len(failed_tests)
         eprint("{} out of {} tests succeeded".format(nr_succeeded, nr_tests))
-        if nr_tests > nr_succeeded:
+        if len(failed_tests) > 0:
+            eprint(
+                "The following tests have failed:\n - {}".format(
+                    "\n - ".join(failed_tests)
+                )
+            )
             sys.exit(1)
 
 
 @contextmanager
 def subtest(name: str) -> Iterator[None]:
     global nr_tests
-    global nr_succeeded
+    global failed_tests
 
     with log.nested(name):
         nr_tests += 1
         try:
             yield
-            nr_succeeded += 1
             return True
         except Exception as e:
+            failed_tests.append(
+                'Test "{}" failed with error: "{}"'.format(name, str(e))
+            )
             log.log("error: {}".format(str(e)))
 
     return False
@@ -879,7 +887,7 @@ if __name__ == "__main__":
     exec("\n".join(machine_eval))
 
     nr_tests = 0
-    nr_succeeded = 0
+    failed_tests = []
 
     @atexit.register
     def clean_up() -> None: